This invention relates to a locking device for a pre-tensioner for a vehicle safety belt, which term includes a safety harness, and more particularly relates to a locking device, for use with a pre-tensioner where the triggering mechanism of the pre-tensioner is mounted on a movable seat, the locking device being intended to prevent unintentional triggering of the pre-tensioner subsequent to a forward movement of the seat relative to the vehicle.
It has been proposed previously to provide a pre-tensioner for use with a vehicle safety belt, to tighten the safety belt in the event of very severe braking, or in the event of a collision. The pre-tensioning of the belt will serve to hold the person secured by the belt firmly in their seat, to prevent the person being thrown forward in the vehicle. The pre-tensioner includes a triggering arrangement, sensitive to deceleration of the vehicle, to indicate operation of the pre-tensioner. Such a pre-tensioner is disclosed in European Publication No. 0239925, and in U.S. Pat. No. 4,768,809, the contents of which are incorporated herein by way of reference.
If the pre-tensioner assembly, incorporating the triggering arrangement, is mounted on a movable seat, there is a risk that the triggering arrangement may be unintentionally actuated if the seat is moved forwards quickly and is then stopped abruptly, for example if the position of the seat is adjusted by a person sitting on the seat, and the seat is moved swiftly forward until it engages the stop provided at the end of the track on which the seat is mounted.